Postage meters (hereinafter called "meters") are well known devices for printing postage impressions of desired value. A meter generally has a set of registers, a print mechanism, and a controlling mechanism. The controlling mechanism acts to interlock the print mechanism and registers to ensure that all postage printed is accounted for. The registers, the print mechanism, and the meter controller are enclosed within a secure housing so as to be inaccessible to the user.
In modern electronic meters, the controlling mechanism is a microprocessor (hereinafter called "meter controller") and the registers are implemented as locations in random access memory (hereinafter called "meter memory"). The meter memory can be expanded to include accounting, cost allocation, or non-revenue information. External and permanently affixed to the housing is a keyboard for data entry to the meter controller and a display for data output to the user. In addition, an input/output port (hereinafter called "I/O port") may be provided so the meter controller can communicate with external devices. Many prior security measures are retained or improved. For example, the meter housing is still utilized to maintain physical security. The meter controller may utilize new techniques unique to electronic equipment to increase security for the meter memory.
In a typical configuration the meter is placed on a base from which it derives power. The base performs envelope handling and similar functions, and may include an input/output facility (hereinafter called "I/O device"). The I/O device can communicate with the meter through the meter's I/O port. The I/O device can also communicate with other peripherals external to the base such as scales and printers. For example, a scale may be used to weigh an article, calculate the cost of sending the article through the mail, and send that cost to the I/O device. The I/O device then tells the meter the denomination of postage to print. A user can also use an external user interface, such as the keyboard and display on a scale, to command the I/O device to generate a preprogrammed report. The I/O device then queries the meter for certain accounting or non-revenue information contained in the meter memory, formats that information, then commands a printer to print the report. However, in each case the meter does not initiate any commands to the I/O device, the meter merely responds to commands from the I/O device.